PortWine Stains (PWS) are congenital disorders of the skin in which vascular malformations produce red-colored isolated lesions occurring most commonly on the face, trunk and neck. The lesion is basically an area of localized enlarged and ectatic blood vessels in the upper dermis. PWS tends to progress from a pale pink and flat lesions in childhood to nodular and dark red-purple lesions in adulthood. Its unpleasant cosmetic appearance causes psychological stress and makes the patient seek medical help. The goal of PWS treatment is to restore the normal color of the skin by selectively destroying the enlarged blood vessels while keeping the rest of the cutaneous structures intact.
The prior art method of choice for treatment of PWS is photocoagulation of the enlarged blood vessels. Ideally, absorption of the laser light by hemoglobin increases the temperature of the abnormal blood vessels until coagulation of blood and vessel walls takes place. Wavelengths for treatment of PWS are usually selected because of their high absorption by hemoglobin. The argon laser with lines at 488 and 514.4 nm has been selected for treatment of PWS because of its high absorption in blood. Recently better coupling has been achieved by matching a pulse dye laser to the 577 nm peak of oxygenated hemoglobin. However, coagulation of the enlarged vessels has been demonstrated at other wavelengths such as 1.06 and 10.6 .mu.m.
Ideally, laser treatment should selectively destroy dermal blood vessels up to a depth of approximately 0.6 mm without causing damage to the epidermis, and especially to the epidermal-dermal layer since damage to this layer disturbs the healing process and may lead to scarring. Epidermal melanin, however, is also an important chromophore with strong absorption in the ultraviolet that decreases through the visible spectrum. Melanin, therefore, has been a potential barrier for the incident laser light causing hearing of the epidermis and reducing the amount of light which reaches the underlying blood vessels.
One of the most recent lasers for the treatment of PortWine Stain is the pulsed dye laser tuned to 577 nm, which is at one of the high absorption peaks of hemoglobin. At 577 nm absorption by epidermal melanin and scattering by the dermis is lower than at the 540 nm peak or at argon wavelengths. The rate of heat generation is higher in the blood vessels than in the epidermis. Although pulse durations of 1 .mu.s or less cause microvascular hemorrhage, 360 .mu.s pulses seem to be very effective in causing selective vascular damage without excessive damage to the epidermis or non-vascular dermal structure. Although investigators report no scarring or any apparent epidermal damage after treatment of PWS lesions with 360 .mu.s pulse 577 nm dye laser, at a dose of 6.5 to 10 J/cm.sup.2, only an overall lightening of 42% has been obtained in the PWS lesions after the initial treatment, and retreatment sessions improved the overall lightening to 68%. Higher energy doses per treatment may produce unwanted epidermal or dermal damage.
A pulsed dye laser system is expensive for an average Dermatologist with a limited purchasing power. However, in the treatment of vascular lesions the coherence of the laser beam is not a critical consideration as long as a light source with proper powers at the right wavelengths can be focused onto the skin with spot sizes in the range of 3-5 mm in diameter (similar to the spot sizes reported in such applications).
The tunable dye laser based systems have been very effective in exploring the mechanisms of the PWS treatments. At the present, the purchasing cost of such laser based systems is approximately $150,000 and the annual maintenance is estimated to be $25,000 per laser system. Consequently, most Dermatologists can not justify the high cost of purchasing a laser based systems for this application. Another cost consideration is the patients who may not be able to afford the high costs of such treatments. Therefore, there is a need for a low-cost system to achieve the same treatment for a much lower cost than the present treatment cost. Such a system is provided by the present invention, described in greater detail below.